Not every VA claim needs a nexus letter. Before you spend money on one, it's worth understanding when they're necessary and when they're not.
You probably don't need a nexus letter if your condition is presumptive. The PACT Act expanded presumptive service connection for dozens of conditions related to burn pit exposure, Agent Orange, and Gulf War service. If your condition is on the presumptive list and you served in a qualifying location during a qualifying period, the VA should grant service connection without requiring a nexus opinion. Check with your VSO first.
You also may not need one if your service treatment records clearly document your condition during active duty and you still have it today. If you were diagnosed with tinnitus in service, you have a current diagnosis, and there's a continuous record, the VA can connect those dots on their own.
Where nexus letters become critical is when the connection isn't obvious from the records alone. That includes conditions that developed years after separation, secondary claims where you're linking a new condition to an existing service-connected disability, claims where the C&P examiner gave a negative opinion and you need to counter it, and conditions where the VA acknowledged your diagnosis but said there's no link to service.
A nexus letter is also important when your service treatment records are incomplete. If your records were lost, destroyed, or just don't document what happened to you, a nexus opinion that connects your current condition to your described service history through medical reasoning can fill that gap.
The bottom line: if the VA can see the connection clearly from your records, save your money. If there's any gap between your service and your current diagnosis that needs medical reasoning to bridge, a nexus letter is probably worth it.
$50 record review fee at intake. $350 only if we can support your claim.